The hub is a cylindrical metal part, the center of which is installed on the shaft to support the inner contour of the tire. Also called rims, rims, wheels and tire bells. Rim refers to the inside of the railway wheel profile. The outline of a wheel consists of a tread and a rim.

Generally speaking, the rim will contact the outer rail of the curve only when the curve passes. In mountainous areas with many curves and small radius, the problem of premature wear of rim and outer rail often occurs, and measures need to be taken to reduce wear. For example, the transverse connection device between worn tread wheels, flange oilers, bogies and radial bogies is used.

Extended data

Gears can be classified according to tooth profile, gear shape, tooth line shape, surface where gear teeth are located and manufacturing method.

1. Gear can be divided into tooth profile curve, pressure angle, tooth height and displacement according to tooth profile.

2. Gears are divided into cylindrical gears, bevel gears, noncircular gears, racks and worm wheels according to their shapes.

3. Gears are divided into spur gears, helical gears, herringbone gears and curved gears according to the tooth line shape.

4. According to the face gear where the gear teeth are located, it is divided into external gear and internal gear. The tooth top circle of external gear is larger than the tooth root circle; While the tooth top circle of the internal gear is smaller than the tooth root circle.